1. Technical Field
The present disclosure relates to an apparatus for correcting an offset of a current sensor. More specifically, the present disclosure relates to an apparatus for correcting an offset of a current sensor that is capable of effectively preventing a pulsation in an output torque in controlling an electric motor in such a manner that a DC offset of a current sensor is corrected while the electric motor is being driven, which may cause the pulsation in the output torque when a current is measured using the current sensor.
2. Description of the Related Art
Recently, a hybrid electric vehicle (HEV) and an electric vehicle (EV) are attracting attention as eco-friendly vehicle. HEVs employ an electric motor driven by electricity, in addition to a traditional internal combustion engine as power sources.
Specifically, an internal combustion engine works as a primary power source, while an electric motor works as a secondary power source by inverting a DC power from a battery to a AC power by an inverter.
EVs have an electric motor only as a primary power source. The motor may be supplied with an AC power inverted by an inverter from a DC power. For HEVs and EVs, an electric motor control unit (MCU) controls precisely an electric motor based on a detected output torque, a sensed current flowing in the motor, and the like.
There may be a difference between a current flowing in an electric motor sensed by a current sensor (hereinafter referred to as “electric motor current”) and a current actually flowing in the motor. This difference is referred to as an “offset” of the current sensor. The offset of the current sensor is a small amount of current necessary for operating the current sensor. Since the electric motor current sensed by the current sensor includes a current actually flowing in the electric motor plus the offset, it is necessary to compensate for the offset in the electric motor current.
If an electric current is provided to the control unit (MCU) without compensating for the offset, pulsation of the output torque of the electric motor may occur due to an error between the electric motor and a current actually flowing. As a result, the entire system may become unstable.
To avoid this problem, it is typical to set an offset in advance at the beginning of driving the motor and then compensate for the offset of the current sensed by the current sensor. However, the offset is likely to vary due to an external noise, elapse of years, an ambient temperature change, the current sensor aging, etc.
Therefore, via the conventional static offset compensation, there eventually occurs an error between the sensed current and the actual current. This may result pulsation in the output torque of the motor output, and thus the motor cannot be controlled stably. Further, if the physical resonation point of the entire system such as an EV is in synchronization with the pulsation frequency of the output torque, the EV may become unstable.